Python: default to Python 3.8 (#17798)
Python: default to Python 3.8 (#17798)


LLNL/spack,LLNL/spack,iulian787/spack,iulian787/spack,iulian787/spack,iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack,LLNL/spack